This invention relates to CMP processes for use in fabrication of integrated circuits generally, and specifically to CMP used to fabricate a non-volatile resistance RAM structure and CMOS processes to make the memory devices, particularly CMR/PCMO devices.
Colossal Magnetoresistance (CMR) materials, such as Pr0.7CaO0.3MnO3 (PCMO) for example, have been found to have varying resistance states depending on the polarity and strength of an electric pulse passed through the material. These types of material may be used for novel non-volatile resistance random access memory (RRAM) applications. However, the integration of CMR films into CMOS ICs remains a challenge.
Know techniques for incorporation of CMR materials into CMOS ICs include the use of a damascene structure along with chemical mechanical polishing (CMP), which has been used to pattern CMR films into a CMOS circuit, as shown in FIG. 1. A commercially available slurry, silica plus NH4OH, which is generally used to polish SiO2, however, this slurry is not known to have been used in the CMP of CMR films. As is to be expected, CMP selectivity between CMR films and SiO2 films is poor. That means that CMP of CMR films will not stop on the underlying oxide, such as tetraethylorthosilicate oxide (oxane) TEOS film. This leads to over polishing of CMR films and makes CMR thickness control difficult. Additionally, because of the high PCMO processing temperature, e.g., 500xc2x0 C. to 650xc2x0 C., required to form proper PCMO structure for RRAM applications, there is some inter-reaction at the SiO2/PCMO interface, which makes thickness measurement of SiO2 unreliable. This characteristic of CMR CMP has precluded the use of SiO2 thickness measurements to determine the end point of CMP CMR films and also for controlling CMR film thickness.
A PCMO thin film has been grown on both epitaxial YBa2Cu3O7 (YBCO) and partial epitaxial Pt substrates via pulsed laser abrasion (PLA) technique, Liu et al., Electric-pulse-induced reversible resistance change effect in magnetoresistive films, Applied Physics Letters, 76, 2749, 2000; and Liu et al., U.S. Pat. No. 6,204,139, granted Mar. 20, 2001, for Method of switching the properties of perovskite materials used in thin film resistors. X-Ray diffraction (XRD) polar figures confirm the epitaxial properties of PCMO thin films. Liu et al., A new concept for non-volatile memory: the electric-pulse induced resistive change effect in Colossal Magnetoresistive thin films, JPL Publication 01-15; Non-Volatile Memory Technology Symposium 2001; November, 2001, pp 18-24, provides additional research information in the field of CMR-containing integrated circuits.
U.S. Pat. No. 6,204,139 describes the resistance change which occurred when electric pulses are applied at room temperature to PCMO thin films. The PCMO thin films were deposited on both epitaxial YBa2Cu3O7 (YBCO) and partial epitaxial Pt substrates by pulsed laser deposition (PLD). The polarity of the electric pulse determines the character of the resistance change, i.e., increase or decrease.
A method of CMP thin films during fabrication of IC devices includes preparing a substrate, including building IC component structures on the substrate; depositing a bottom electrode on the substrate; depositing a first CMP layer having a first known CMP selectivity on the substrate; patterning the first CMP layer to form a pattern having a lower margin; forming indicator structures on the first CMP layer in the pattern; depositing a second CMP layer having a second known CMP selectivity relative to that of the first CMP layer, including depositing portions of the second CMP layer in the pattern of the first CMP layer; CMP the structure so that the indicator structures are removed and any portion of the first CMP layer and second CMP layer are removed to a level corresponding to the lower margin; and completing the IC structure.
It is an object of the invention to provide an indicator useful in CMP of integrated circuit component layers having poor CMP selectivity.
Another object of the invention is to provide a method for CMP of CMR materials formed on oxide layers or nitride layers.
A further object of the invention is to provide for CMP of CMR materials with a silica and ammonium hydroxide slurry.